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Systems · Advanced · 2 min read

Nutrient film technique (NFT)

In NFT a thin, continuous film of nutrient solution runs down sloped channels past bare roots. It is efficient and well proven for lettuce and herbs, but large cannabis root masses can dam the channel, and roots dry within one to three hours if the pump stops. Keep flow continuous (about 1–2 L/min per channel), slope about 1:30 to 1:100, and solution at 18–22 °C.

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Draft: awaiting expert review Updated
VegFlowerNFT

Being reviewed. Our editors are double-checking a few figures in this article against primary sources. Marked passages may change.

Short answer. A pump sends a thin film of solution down a gently sloped channel; roots sit in the film with their upper surface in air, so they get water and oxygen at once. It is a mature system for leafy greens [1][2]. For cannabis it works best for clones, mothers, short-veg SOG and small plants; big flowering plants build root mats that dam the channel, and the system has almost no buffer: roots can dry in 1–3 hours without flow [4].

Numbers that matter

Parameter Target Notes
Flow per channel 1–2 L/min Jardin defaultbeing reviewed
Slope 1:30–1:100 (1–3 %) being reviewed
Channel length ≤ 10–15 m Long channels deplete O₂ and nutrients at the far end
Film depth A few mm Deep, slow film = root rot
Solution temperature 18–22 °C (64–72 °F) [3]
pH / EC pH 5.6–6.0; EC as DWC
Lights-off Reduce flow if desired, never stop [4]

How to run it

  1. Wide, flat-bottomed channels for cannabis; lids that block light.
  2. Start plants in rockwool or a small net pot so the root ball sits in the film.
  3. Confirm return flow at every channel daily (or by sensor).
  4. Prune or redistribute root mass if it starts to pond.
  5. Backup pump on the same manifold if you can.

Failure modes

Problem Sign Jardin response [4]
Pump failure No return flow, wilting within hours Switch to backup pump; escalate alert
Channel blocked by roots Water at the inlet end rises/overflows Inlet high float → pump off, "channel blocked"
Film too deep/slow Brown roots at outlet end Flow and temperature trend
Warm solution Root rot Chiller, shade the channels

Jardin notes

Jardin method "NFT": flow meter on the return is the proof that a film exists; pump current; inlet-end high float; a 30 s loss of return flow with pump current = blockage or split; with zero current = pump dead. Automation level 3 [4].

Safety

Water + electricity: GFCI/RCD, drip loops, leak trays under the reservoir.

Common mistakes

  • Using lettuce channels for big flowering plants.
  • Narrow channels that dam within weeks.
  • No flow alarm.

Evidence

NFT for leafy crops is Established [1][2]. NFT for full-size flowering cannabis is Grower practice with no published comparisons we can cite.

Questions this article answers

Does NFT work for cannabis?

NFT works for cannabis clones, mothers, short-veg sea-of-green and small plants, but it struggles with full-size flowering plants. Large cannabis root masses build mats that dam the channel, and roots can dry within 1–3 hours if flow stops. NFT is well established for lettuce and herbs, while NFT for big flowering cannabis remains grower practice with no published comparisons.

What flow rate for an NFT channel?

An NFT channel for cannabis typically runs about 1–2 litres per minute of continuous flow, a starting default similar to leafy-green guidance that should be verified per system. The film should be only a few millimetres deep, since a deep, slow film causes root rot. At lights-off you can reduce flow, but never stop it, and confirm return flow at every channel daily.

What slope should NFT gullies have?

NFT gullies should slope about 1:30 to 1:100, which is a 1–3% fall, so solution runs as a thin film past the roots; check the figure against hydroponic reference texts. Keep channels no longer than about 10–15 metres, because long runs deplete oxygen and nutrients at the far end. Use wide, flat-bottomed, light-proof channels for cannabis.

What happens if my NFT pump stops?

If an NFT pump stops, the thin film drains away and bare cannabis roots can dry out within 1–3 hours, so plants wilt within hours. NFT has almost no buffer, unlike media-based systems. Fit a flow alarm on the return, put a backup pump on the same manifold if you can, and confirm return flow at every channel daily or by sensor.

Sources

  1. Cornell CEA. Hydroponic lettuce handbook. cea.cals.cornell.edu/
  2. Resh HM, 2022. Hydroponic Food Production, 8th ed. CRC Press (NFT chapter). doi.org/10.1201/9781003133254
  3. Colorado State University Extension PlantTalk 2043. Root disease problems and management in hydroponic systems. planttalk.colostate.edu/topics/miscellaneous/2043-root-disea
  4. GenetixBay Jardin engineering notes, 2026 (system profiles and failure margins)..

Related

SupportedIntermediate · Draft

Deep water culture (DWC)

In DWC roots hang in an aerated nutrient solution. It grows fast but depends on two things: dissolved oxygen (keep above about 6 mg/L, ideally near saturation) and solution temperature (18–22 °C / 64–72 °F). Warm, poorly aerated water is how Pythium root rot starts. Run pH 5.6–6.0 and EC 0.8–2.0 mS/cm by stage, and treat the air pump as life support.

Grower practiceAdvanced · Draft

Recirculating deep water culture (RDWC)

RDWC links several DWC sites to a control bucket and circulates the solution with a pump, so one reservoir sets pH, EC and temperature for every plant and a single chiller cools the lot. It adds circulation and plumbing failure modes to DWC's oxygen and temperature risks. Targets match DWC: 18–22 °C, DO above 6 mg/L, pH 5.6–6.0.

SupportedIntermediate · Draft

Low-pressure aeroponics (LPA)

LPA uses an ordinary submersible pump and spray heads to drench roots hanging in a dark chamber with coarse droplets. It is essentially a spray-assisted hydro system: forgiving (a pool on the chamber floor keeps roots wet for hours), cheap, and easier than true high-pressure aeroponics. Run sprays continuously or on short cycles such as 1 minute on, 4 off, with a chamber humidity watchdog and solution at 18–22 °C.

Grower practiceBeginner · Draft

Choosing your growing system: soil, coco, rockwool or hydro

Choose by how much attention and measurement you can give, not by yield claims. Soil and living soil forgive mistakes for days; coco and drip need daily feeding; DWC, NFT and aeroponics grow fast but can lose roots within hours if a pump or air supply fails. No controlled study shows one system out-yielding the others when light and climate are equal.

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